1. Field of the Invention
This invention relates to a method and apparatus for automatic fabrication of three-dimensional objects from a plurality of individual layers of fabrication material stacked together in sequence to form the object. More particularly, the invention relates to the use of a substrate to convey each layer to a station where these layers are affixed to each other and then the substrate is removed.
2. Background Discussion
The idea of automatic fabrication of three-dimensional solid objects dates back at least to the 18th century, when a pantograph-like device was used in France to copy medallions. James Watt later built several machines, based on the same principal, capable of carving full human busts. Over the past 45 years, machining, lathe-turning and grinding devices have been placed under computer control (called "CNC" for "computer-numerical control") to allow the generation of original shapes from designs entered into computers by engineers using computer-aided design (CAD) software. These processes are called "subtractive" fabrication, because they start with a solid block of material and generate the desired shape by removing material from the block.
Since the subtractive processes work by applying a cutting tool to a solid block, they have the common disadvantage of being limited in the shapes that they can generate. Intricate or nested structures are difficult or impossible to build by these methods. A more modern approach is "additive" fabrication in which a fluid or powdered material is solidified or congealed in successive small regions or layers to form the desired object. This idea goes back at least to the photo-relief process of Baese (U.S. Pat. No. 774,549), and has been substantially refined through dual-laser photopolymerization of Swainson (Danish Patent Application 3611), liquid droplet deposition of Masters (U.S. Pat. No. 4,665,492), single-laser photopolymerization of Andre (French Patent Application 84 11241) and Hull (U.S. Pat. No. 4,575,330), masked-lamp photopolymerization of Fudim (U.S. Pat. No. 5,135,379), laser sintering of Feygin (U.S. Pat. No. 4,752,352) and Deckard (U.S. Pat. No. 4,863,538), and robotically guided extrusion of Crump (U.S. Pat. No. 5,121,329).
There are also several hybrid processes which combine additive and subtractive processes. Usually this involves cutting or etching the contours of individual layers of an object, and stacking and binding the contours. The earliest use of such a process is that of Morioka (U.S. Pat. No. 2,015,457), and more recent refinements have been made by DiMatteo (U.S. Pat. No. 3,932,923), Feygin (U.S. Pat. No. 4,752,352), Kinzie (U.S. Pat. No. 5,015,312), and Berman (U.S. Pat. No. 5,071,503).
A Swedish company, Sparx AB, manufactures a manual system which uses a substrate to carry a foam sheet of fabrication material bonded to the substrate. Individual layers of material are formed by cutting through the material, removing negative regions, and, prior to affixing successive layers, removing the substrate.
All of the prior additive and hybrid processes suffer from several or all of the following drawbacks:
(1) Accuracy and resolution are limited to the domain of about 0.1 millimeters (0.004 inch). One reason is the difficulty of controlling the action of a laser beam (whether for irradiating, as in Hull or Deckard, or for cutting, as in Feygin), a particle jet (as in Masters), or an extrusion head (as in Crump), plus the difficulty of compensating for the width of the laser beam, jet stream or extrusion bead. Another reason is the minimum thickness of a single layer that can be formed from the raw material liquid or powder, or the minimum thickness of the extrusion bead that can be laid down. PA1 (2) In the fully additive processes, large regions of solid material take a long time to fabricate, slowing down the process for building structures with such large solid regions. PA1 (3) All of the processes are difficult and expensive to scale up for fabrication of large objects, because they involve complicated mechanisms of laser optics or robotics. PA1 (4) All of the processes call for fabrication specifically in very thin layers, which limits the fabricator speed unnecessarily in cases where great resolution in the vertical direction is not necessary. In many instances, fabricator users would like to get a fast, low resolution, rendition of the desired object, but none of the prior art provides a way to achieve this. PA1 (5) Only Kinzie and Crump provide a way to achieve a mixture of colors in the object generated. Kinzie requires a secondary printing process on a special absorbent or translucent material to achieve this, and Crump requires the use of specially died materials. PA1 (6) All of the processes always produce a solid object in a permanently fixed configuration, such that any fracturing or cross-sectioning of the object is tantamount to destroying it. No means has ever been provided for generating an object which can be temporarily taken apart into sections and easily reassembled with no loss of integrity. PA1 (7) The raw materials for most of the processes are specialty chemicals which are expensive and, in some cases, are toxic or require special handling to prevent combustion. PA1 (8) Many of the processes are limited to working with certain types of materials such as only photopolymers in the simple photocuring methods, or only thermally softenable materials in laser sintering. PA1 (9) Most of the processes hide the object being built in an opaque solid or a murky liquid environment, depriving the fabricator user from the pleasure and benefit of watching the object take shape. PA1 (10) All of the processes, except that of Sparx AB, use complicated and expensive mechanisms and/or electro-optical devices, making fabricators based on them large, heavy, expensive and difficult to maintain. PA1 (1) Accuracy and resolution can both be easily achieved in the domain of about 0.05 millimeters (0.002 inch). This can be further reduced to less than about 0.01 millimeters (0.0004 inch) with specially accurate cutting or positioning mechanisms and very thin materials. PA1 (2) In several embodiments of this invention in which layers of the desired object are cut from sheet material, large regions of solid material are fabricated very quickly because they only require cutting around the periphery. PA1 (3) In embodiments of this invention in which layers of the desired object are cut from sheet material, it is easy to scale up to build large objects. This is because the required mechanisms and components are quite simple and, in many cases, are already available for other purposes in large size formats. PA1 (4) Thicker layers of materials are used when vertical resolution can be sacrificed for speed. This option is analogous to the "draft mode" available on dot matrix printers to achieve fast, low resolution, output. A means (angular cutting) is also provided for ameliorating this reduction of resolution. PA1 (5) Colors can be easily incorporated and mixed in any desired degree of complexity in the fabricated object. For several embodiments, in which layers of the desired object are cut from sheet material, at least 60 colors are already available. PA1 (6) In one variation of the method of this invention, fabricated objects are not permanently fixed, but can be easily separated at any one or more of many cross sections. The resulting sections can then be easily rejoined to form again the complete object. The object can be thus separated and rejoined at the same or different cross sections, repeatedly and without limitation. PA1 (7) For several embodiments of this invention in which layers of the desired object are cut from sheet material, the raw materials are readily available and include inexpensive varieties. The materials are nontoxic and have no special handling or storage requirements. PA1 (8) A wide variety of materials may be used in the process, including, metals, plastics, ceramics, and composites. PA1 (9) The method of this invention can be practiced so as to leave the object being built visible during the fabrication process, providing the user with the pleasure and benefit of watching the object take shape. PA1 (10) The method can be embodied using simple and inexpensive mechanisms, so that the fabricator equipment can be relatively small, light, inexpensive and easy to maintain. PA1 (a) providing a station were the successive individual layers are stacked together, PA1 (b) placing on a carrier substrate a first individual layer of fabrication material, PA1 (c) conveying the first layer of fabrication material on said carrier substrate to said station and transferring to said station, PA1 (d) separating the carrier substrate from the fabrication material, exposing a bonding surface on said first individual layer to which a successive individual layer is affixed, PA1 (e) placing on the carrier substrate a second layer of fabrication material and conveying the second layer of fabrication material on the carrier substrate to said station, PA1 (f) aligning said individual layers and bringing said bonding surface on said one individual layer into contact with said successive individual layer so that said layers become affixed together, PA1 (g) separating said carrier substrate from the fabrication material after affixing said one individual layer to said successive layer, exposing a bonding surface on said successive individual layer to which another successive fabrication layer is affixed, and PA1 (h) repeatedly aligning and then affixing successive fabrication layers together after conveying said successive fabrication layers on the carrier substrate in series to the station until said object is formed, first affixing individual successive fabrication layers together and then separating the carrier substrate from each individual, successive fabrication layer.
The ultimate commercial importance of automatic fabrication of three-dimensional objects is hampered by these disadvantages.